I have a very basic system as I grow. For now I have a large marine 12v battery connected to a 2000 watt inverter (it's all I've got).I keep it charged with my garage battery charger. Everything works fine.

Can I connect the center tap of my Vanner Equilizer to the positive terminal battery and battery ground to the chassis and charge my 12v while driving?

We hope to keep the refrigerator on while on the road. Works fine now,but I don't think I'll get a lot of hours without killing the battery unless I can keep it charged.

Dave

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I couldn't repair my brakes, so I made my horn louder.1989 MCI-102 A3DD 6V92 Turbo, AlisonTons of stuff to learn!Started in Cheboygan, Michigan (near the Mackinaw Bridge). Now home is anywhere we park

A Vanner equalizer is intended to maintain a charge on a set of batteries wired in series and parallel such that the batteries provide for loads of both 12 and 24 volts. A good example is the chassis batteries on a Prevost.

Most conversions now being built are set up so the house systems have both 12 and 24 volts available also. Those 12/24 volt systems can be discharged unequally so the Vanner equalizer does exactly as its name implies and assures all batteries in the set are equally charged.

If you ever wondered what is inside a Vanner equalizer, here is the patent circa 1982 - the timeframe when most of our Vanner equalizers probably were produced. http://www.google.com/patents/US4479083 Fig 7 is the schematic for the electron pushers

The concept is simple - a precision voltage divider formed by R12 and R13, a pair of 1% resistors, is connected between the 24 volt input and ground, and derives a reference voltage of 50% of the input voltage. That is used to control the output of an autotransformer that is fed by a switching power supply that produces the output current on the 12 volt tap.

There is no reason a Vanner equalizer can't be used to generate current to charge a 12 volt battery, but you have to connect it properly. One point - it can't be used as an equalizer and a converter (the configuration that charges a battery) at the same time, it can do one or the other.

When connected as an equalizer it has two 12 volt batteries connected, one is the "loaded" battery connected between ground and +12V, and the other is the "source" battery, connected between the +12V and the +24V terminals (loaded and source are my terms, not Vanners). In this situation both batteries get charged from the 24 volt source and the Equalizer forces the voltage to remain exactly equal (within 1%) between them. All 12 volt loads are connected to the loaded battery. If a load is present (you turn on some lights or a radio or whatever) the current to the load comes from the loaded battery, but that pulls it's voltage down below 50% of the 24 volt voltage. The Equalizer supplies half of the load current from the 24 volt source (if the alternator is running) or from the "source" battery if not. That makes it look like the two 12V batteries are in parallel and each is supplying half the current. They aren't really in parallel, of course - they are supplying power not only to the load, but also to the switching power supply that is creating the current to equalize the load on the pair of batteries. The key point here is that there are always a pair of batteries connected to the terminals of the Vanner, they are equal in size and capacity, and they always stay at the same voltage level and are therefore equally charged.

If you connect the Vanner as a converter, you supply it with a 24 volt source and it puts out a 12 volt current on it's 12 volt terminal. In this case, the loaded battery is separate from the 24 volt supply. You do not have a pair of 12 volt batteries connected with the center tap connected to the Vanner's 12 volt terminal, you just have one loaded battery and a separate 24 volt source (which could be an alternator and a set of start batteries in the case of a bus). Here, the Vanner takes in current on it's 24 volt terminal, divides it very accurately in half and sends it out on the 12 volt terminal to supply loads, or in this case charge a 12 volt battery. It will do this up to the current limit of the Vanner. If you look on the Vanner manual http://www.vanner.com/manuals/65-60.pdf page 8 there is a diagram labeled "Caution Adding 12V Batteries" and the left hand diagram titled "acceptable" is the setup you want. If you look at that diagram, the bus alternator is on the left, the bus start batteries are Battery A and Battery B, and the house batteries are on the right.

I hope this helps. I spent a half hour figuring this out, finding the Vanner patent and schematic, and typed up 75% of this reply only to lose it when I pushed the wrong button on the computer...

Edit: I knew I forgot something. Vanners are always on. They always draw current. If you leave a Vanner connected to a pair of batteries it will discharge them down to zero. It will do it slowly, with perfect equalization, and when you come out to check on your batteries they will both be discharged to around 1 volt. It happened to me... Disconnect the Vanner if you leave the bus without a charger on.

I wanted to run my 12v loads directly off my 100 AMP Vanner. The thing kept going into a fault mode. I was on the road and bought a battery to use as a buffer between the Vanner and the loads. That was several years ago and it has been charging this battery ever since.

John

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If It Can't Be Grown Then It Has To Be MinedJohn RiddleWells NV1984 MC9

I have owned Prevost coaches for 23 years. I never turn off the chassis main disconnect switches. My coaches will go 3 or more months without being started or charged and the batteries will still have plenty of power available to start the coach. I don't doubt a Vanner draws power, but it is so little as to be almost meaningless. If your batteries go dead in 2 or three months you have a load other than the Vanner.

I should correct my statement, I guess. The Vanner is always potentially going to be able to draw power. It really only turns on if the 0 - 12 volt battery terminal has a voltage lower than 50% of the 24 volt battery terminal. At that point it draws power from the 24 volt source to raise the voltage of the 12 volt terminal. The reason could be anything, a small load or the 12V battery simply losing it's charge faster than the 24 volt battery. In my case a combination of older batteries and a keep-alive load from a car radio caused the issue. The car radio issue was my fault - it had an "ignition sense" lead to tell it when the car ignition was on or off, and didn't go into it's low power sleep mode unless the car was turned off, regardless of if the radio itself was turned on or off. It's just another thing to keep aware of.

We use the Vanner equalizer as a 12v battery charger. I checked the wiring and it is simply 24v to input, the 12v output to the house bank (I think we have #4 wire), and the ground to chassis. It is always on as long as there is a 24v source. I would guess that Jon does not experience any problem from this because probably his, like ours, is energized through the main switch, so it is really only on when the bus is in use. When parked, the main would be off, and there would be no draw.

We actually have a dash switch also, so it is only on when we choose. The tech at Vanner had told me this was totally unnecessary unless I just liked having an extra switch to play with. I guess I do!